Researchers at Edinburgh University treated zebrafish with drugs which produced a similar reaction to touch or proximity to a predator, leading to increased brain function and production of a protective coating called myelin.

It is too early to say whether increased brain function leads to more myelin production in humans, according to researchers.

Researchers at Edinburgh University treated zebrafish with drugs which led to increased brain function and production of a protective coating called myelin

But other studies have shown that activities such as learning the piano, juggling or doing puzzles stimulates brain growth, Edinburgh University researcher Dr Sigrid Mensch said.

"At the moment we are just looking at brain activity, which is a very complex system, so we couldn't predict that doing crosswords would eventually lead to more myelin," she said.

"But there are other studies that show something like learning the piano or juggling have increased white matter, which is essentially myelinated axons.

"At the moment we have just been looking at a very particular type of brain activity, so we couldn't be sure that crossword-solving would be a treatment.

"The drugs increased the escape response in the zebrafish, which is triggered by the sight of a predator or a touch that leads to increased movement.

"We then saw increased myelin generation, but it's very complex so it might not be translatable to humans."

Myelin protects nerve fibres, known as axons, and speeds up the transfer of information.

Damage to this protective coating is known to contribute to diseases such as MS, which affects balance, movement and vision.

Drugs that suppressed brain function in the zebrafish led to a drop in myelin while drugs that increased brain function boosted myelin by 40%.

Until now, it was not known how brain activity controls production of myelin by specialist cells.

Dr David Lyons, of the University of Edinburgh's Centre for Neuroregeneration, who led the study, said: "We have a long way to go before we fully understand how our brain activity regulates myelin production, but the fact that this is even something that the brain can do is a good news story.

"We are hopeful that one day in the future we may be able to translate this type of discovery to help treat disease and to maintain a healthy nervous system through life."

Dr Emma Gray, head of biomedical research at the MS Society, said: "The more we learn about how myelin production happens in the brain, the more chance we have of developing effective and targeted therapies to repair myelin in people with MS."

The study, published in the journal Nature Neuroscience, was funded by The Wellcome Trust, the Biotechnology and Biological Sciences Research Council and the Lister Research Prize.